The invention relates to a device for assembling a continuous strand of tobacco, including a suction strand conveyor belt which is operationally connected with a suction chamber along an assembly track and which is conducted around a contact wheel that revolves along with the suction strand conveyor belt in the strand inlet area of a shaping arrangement that forms the strand of tobacco into a wrapped strand of cigarettes.
Individual and loosened tobacco fibers usually are sprinkled on a strand conveyor in the shape of an endless conveyor belt revolving in a tobacco channel to form a fiber strand for producing a strand of cigarettes. The strand is continuously transported out of the area of the strand formation and evened out before it is deposited on a strip of wrapping material, for example a strip of cigarette paper, which is moved into a shaping arrangement by means of a revolving shaping belt. The strip of wrapping material enters the inlet area of the shaping arrangement still flat and then is molded into a U-shape around the fiber strand during its passage through the shaping arrangement before it is placed completely around the strand and is closed around the strand, as a rule by gluing, along an overlapping seam to form a cylindrical wrapping.
The suction strand conveyor belt usually comprises an air-permeable textile tape on which tobacco particles can be caught and released again at another location. Because of the applied underpressure and/or because of the mechanical pressure in the course of the compression of the fiber strand, the correct transfer of all particles in the strand to the shaping arrangement is prevented. To assure that all particles in the strand, even those which have become stuck to the strand conveyor, are transferred to the shaping arrangement, the latter has a device for stripping off tobacco particles, a so-called scraper, at its inlet end. The scraper consists of a base body and has a scraper edge, which is positioned closely near the surface of the suction strand conveyor belt and scrapes the tobacco particles of the strand away from the belt. The transfer zone of the tobacco strand in which the fiber strand is transferred from the upper suction strand conveyor belt onto the lower cigarette paper strip, conveyed by the shaping belt into the shaper, should be made as short as possible, or respectively should extend as closely as possible next to the shaping belt.
To this end, good results have been achieved with the use of a contact wheel for reversing the suction strand conveyor belt. The contact wheel, which should be as small as possible, creates large centrifugal forces for the better removal of the tobacco strand and permits an optimal placement and design of a scraper assigned to the suction strand conveyor belt. However, a relatively tightly designed belt reversal is extremely sensitive to tobacco dust that is inevitably generated in this area. The tobacco dust acts destructively on the bearing of the contact wheel and is deposited on the circumferential surface of the wheel, so that the suction strand conveyor belt is lifted off and can be destroyed by the scraper.
An attempt to remove dust deposits from the circumferential surface of the contact wheel by placing the scraper against it has not lead to satisfactory results.